Language:
كتاب الصلاة
8  
Prayers (Salat)
(3)
Chapter: To tie Izar (dress worn below the waist) at one's back while offering Salat (prayers)
(3)
باب عَقْدِ الإِزَارِ عَلَى الْقَفَا فِي الصَّلاَةِ
Sahih al-Bukhari 353

Narrated Muhammad bin Al Munkadir:

I saw Jabir bin `Abdullah praying in a single garment and he said that he had seen the Prophet (ﷺ) praying in a single garment.

حَدَّثَنَا مُطَرِّفٌ أَبُو مُصْعَبٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ أَبِي الْمَوَالِي، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ، قَالَ رَأَيْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ يُصَلِّي فِي ثَوْبٍ وَاحِدٍ وَقَالَ رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم يُصَلِّي فِي ثَوْبٍ‏.‏
Reference : Sahih al-Bukhari 353
In-book reference : Book 8, Hadith 5
USC-MSA web (English) reference : Vol. 1, Book 8, Hadith 349
  (deprecated numbering scheme)